Chavanel, who won stage two, caught team-mate Jerome Pineau on the final climb and went on to win by 57 seconds from Spain's Rafael Valls Ferri.

Britain's Geraint Thomas also faded on the 14km climb up Cote de Lamoura to drop back from second overall to 31st.

Switzerland's Fabian Cancellara, who lead overnight, fell away late on and is now 13 minutes 11 seconds back.

Cancellara had been riding in the peloton as he looked to stay on as leader for one final day before the race headed into the Alps.

Tomorrow I will do everything to defend yellow, but I know that the battle will mainly concern Contador, Schleck and Evans

Sylvain Chavanel

But he laboured up the final hill of the 165.5km stage from Tournus to Station des Rousses, along with sprinters Mark Cavendish and Thor Hushovd.

"I was on the limit," he said. "It was hot, really hot. For me, it was just too much. I just couldn't do any more."

"I've had some great days in the yellow jersey. Tomorrow I'll be back in my normal jersey. Things will be a bit more calm, and less stressful."

Team Sky rider Thomas, who started the day just 20 seconds behind Cancellara, suffered a puncture at the bottom of the final climb and struggled to attach himself to the peloton, losing 5'18".

"It was just so hot and there was a combination of things," conceded the Welshman. "It's not too bad though. I never thought I'd be in that position from the start so it was good to have a go, but I just didn't have it today."

His Sky team-mate Bradley Wiggins looked much more spritely though, finishing 1'40" behind Chavanel, along with the main bunch, which included all the main Tour contenders, including Alberto Contador, Lance Armstrong and Andy Schleck.

His efforts keep him handily placed in 11th overall, 2'35" adrift of the race leader.

"It was a harder day than a lot of people expected," he said. "It was a bit of a stalemate with everyone watching each other and it turned out to be a hard stage but it's good to get one out of the way."

The final climb was also tough on Pineau, who lead a five-man breakaway in the opening kilometre and was first over the first five summits of the day in his pursuit of the King of the Mountains jersey.

But he ran out of steam on the Cote de Lamoura with double polka dot jersey points on offer, allowing his team-mate Chavanel to take the glory.

"Right now I'm on my little cloud, I'm floating and I don't know how else to describe it," said Chavanel.

"I began to think of the yellow jersey on the last climb.

"Tomorrow I will do everything to defend it, but I know that the battle will mainly concern Contador, Schleck and Evans.

Valls Ferri and Rabobank's Juan Manuel Garate also went past the Frenchman, who eventually finished 3'55" down.

The big hitters are expected to begin their serious challenge during Sunday's 189km eighth stage from Station des Rousses to Morzine-Avoriaz.

World champion Evans said: "I think it'll be another day where the main GC contenders are looking at themselves, testing themselves.

"We'll see if someone really wants to lay it on the line and try and blow it apart.

"Someone like Alberto or Lance, it's probably in their best interest to do that. For me, I'll see how they go and how I go."

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